1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
use super::operand::{OperandRef, OperandValue};
use super::place::PlaceRef;
use super::{FunctionCx, LocalRef};

use crate::base;
use crate::common::{self, IntPredicate};
use crate::meth::get_vtable;
use crate::traits::*;
use crate::MemFlags;

use rustc_middle::mir;
use rustc_middle::mir::Operand;
use rustc_middle::ty::cast::{CastTy, IntTy};
use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf};
use rustc_middle::ty::{self, adjustment::PointerCast, Instance, Ty, TyCtxt};
use rustc_span::source_map::{Span, DUMMY_SP};

impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
    #[instrument(level = "trace", skip(self, bx))]
    pub fn codegen_rvalue(
        &mut self,
        mut bx: Bx,
        dest: PlaceRef<'tcx, Bx::Value>,
        rvalue: &mir::Rvalue<'tcx>,
    ) -> Bx {
        match *rvalue {
            mir::Rvalue::Use(ref operand) => {
                let cg_operand = self.codegen_operand(&mut bx, operand);
                // FIXME: consider not copying constants through stack. (Fixable by codegen'ing
                // constants into `OperandValue::Ref`; why don’t we do that yet if we don’t?)
                cg_operand.val.store(&mut bx, dest);
                bx
            }

            mir::Rvalue::Cast(mir::CastKind::Pointer(PointerCast::Unsize), ref source, _) => {
                // The destination necessarily contains a fat pointer, so if
                // it's a scalar pair, it's a fat pointer or newtype thereof.
                if bx.cx().is_backend_scalar_pair(dest.layout) {
                    // Into-coerce of a thin pointer to a fat pointer -- just
                    // use the operand path.
                    let (mut bx, temp) = self.codegen_rvalue_operand(bx, rvalue);
                    temp.val.store(&mut bx, dest);
                    return bx;
                }

                // Unsize of a nontrivial struct. I would prefer for
                // this to be eliminated by MIR building, but
                // `CoerceUnsized` can be passed by a where-clause,
                // so the (generic) MIR may not be able to expand it.
                let operand = self.codegen_operand(&mut bx, source);
                match operand.val {
                    OperandValue::Pair(..) | OperandValue::Immediate(_) => {
                        // Unsize from an immediate structure. We don't
                        // really need a temporary alloca here, but
                        // avoiding it would require us to have
                        // `coerce_unsized_into` use `extractvalue` to
                        // index into the struct, and this case isn't
                        // important enough for it.
                        debug!("codegen_rvalue: creating ugly alloca");
                        let scratch = PlaceRef::alloca(&mut bx, operand.layout);
                        scratch.storage_live(&mut bx);
                        operand.val.store(&mut bx, scratch);
                        base::coerce_unsized_into(&mut bx, scratch, dest);
                        scratch.storage_dead(&mut bx);
                    }
                    OperandValue::Ref(llref, None, align) => {
                        let source = PlaceRef::new_sized_aligned(llref, operand.layout, align);
                        base::coerce_unsized_into(&mut bx, source, dest);
                    }
                    OperandValue::Ref(_, Some(_), _) => {
                        bug!("unsized coercion on an unsized rvalue");
                    }
                }
                bx
            }

            mir::Rvalue::Repeat(ref elem, count) => {
                let cg_elem = self.codegen_operand(&mut bx, elem);

                // Do not generate the loop for zero-sized elements or empty arrays.
                if dest.layout.is_zst() {
                    return bx;
                }

                if let OperandValue::Immediate(v) = cg_elem.val {
                    let zero = bx.const_usize(0);
                    let start = dest.project_index(&mut bx, zero).llval;
                    let size = bx.const_usize(dest.layout.size.bytes());

                    // Use llvm.memset.p0i8.* to initialize all zero arrays
                    if bx.cx().const_to_opt_u128(v, false) == Some(0) {
                        let fill = bx.cx().const_u8(0);
                        bx.memset(start, fill, size, dest.align, MemFlags::empty());
                        return bx;
                    }

                    // Use llvm.memset.p0i8.* to initialize byte arrays
                    let v = bx.from_immediate(v);
                    if bx.cx().val_ty(v) == bx.cx().type_i8() {
                        bx.memset(start, v, size, dest.align, MemFlags::empty());
                        return bx;
                    }
                }

                let count =
                    self.monomorphize(count).eval_usize(bx.cx().tcx(), ty::ParamEnv::reveal_all());

                bx.write_operand_repeatedly(cg_elem, count, dest)
            }

            mir::Rvalue::Aggregate(ref kind, ref operands) => {
                let (dest, active_field_index) = match **kind {
                    mir::AggregateKind::Adt(adt_did, variant_index, _, _, active_field_index) => {
                        dest.codegen_set_discr(&mut bx, variant_index);
                        if bx.tcx().adt_def(adt_did).is_enum() {
                            (dest.project_downcast(&mut bx, variant_index), active_field_index)
                        } else {
                            (dest, active_field_index)
                        }
                    }
                    _ => (dest, None),
                };
                for (i, operand) in operands.iter().enumerate() {
                    let op = self.codegen_operand(&mut bx, operand);
                    // Do not generate stores and GEPis for zero-sized fields.
                    if !op.layout.is_zst() {
                        let field_index = active_field_index.unwrap_or(i);
                        let field = if let mir::AggregateKind::Array(_) = **kind {
                            let llindex = bx.cx().const_usize(field_index as u64);
                            dest.project_index(&mut bx, llindex)
                        } else {
                            dest.project_field(&mut bx, field_index)
                        };
                        op.val.store(&mut bx, field);
                    }
                }
                bx
            }

            _ => {
                assert!(self.rvalue_creates_operand(rvalue, DUMMY_SP));
                let (mut bx, temp) = self.codegen_rvalue_operand(bx, rvalue);
                temp.val.store(&mut bx, dest);
                bx
            }
        }
    }

    pub fn codegen_rvalue_unsized(
        &mut self,
        mut bx: Bx,
        indirect_dest: PlaceRef<'tcx, Bx::Value>,
        rvalue: &mir::Rvalue<'tcx>,
    ) -> Bx {
        debug!(
            "codegen_rvalue_unsized(indirect_dest.llval={:?}, rvalue={:?})",
            indirect_dest.llval, rvalue
        );

        match *rvalue {
            mir::Rvalue::Use(ref operand) => {
                let cg_operand = self.codegen_operand(&mut bx, operand);
                cg_operand.val.store_unsized(&mut bx, indirect_dest);
                bx
            }

            _ => bug!("unsized assignment other than `Rvalue::Use`"),
        }
    }

    pub fn codegen_rvalue_operand(
        &mut self,
        mut bx: Bx,
        rvalue: &mir::Rvalue<'tcx>,
    ) -> (Bx, OperandRef<'tcx, Bx::Value>) {
        assert!(
            self.rvalue_creates_operand(rvalue, DUMMY_SP),
            "cannot codegen {:?} to operand",
            rvalue,
        );

        match *rvalue {
            mir::Rvalue::Cast(ref kind, ref source, mir_cast_ty) => {
                let operand = self.codegen_operand(&mut bx, source);
                debug!("cast operand is {:?}", operand);
                let cast = bx.cx().layout_of(self.monomorphize(mir_cast_ty));

                let val = match *kind {
                    mir::CastKind::PointerExposeAddress => {
                        assert!(bx.cx().is_backend_immediate(cast));
                        let llptr = operand.immediate();
                        let llcast_ty = bx.cx().immediate_backend_type(cast);
                        let lladdr = bx.ptrtoint(llptr, llcast_ty);
                        OperandValue::Immediate(lladdr)
                    }
                    mir::CastKind::Pointer(PointerCast::ReifyFnPointer) => {
                        match *operand.layout.ty.kind() {
                            ty::FnDef(def_id, substs) => {
                                let instance = ty::Instance::resolve_for_fn_ptr(
                                    bx.tcx(),
                                    ty::ParamEnv::reveal_all(),
                                    def_id,
                                    substs,
                                )
                                .unwrap()
                                .polymorphize(bx.cx().tcx());
                                OperandValue::Immediate(bx.get_fn_addr(instance))
                            }
                            _ => bug!("{} cannot be reified to a fn ptr", operand.layout.ty),
                        }
                    }
                    mir::CastKind::Pointer(PointerCast::ClosureFnPointer(_)) => {
                        match *operand.layout.ty.kind() {
                            ty::Closure(def_id, substs) => {
                                let instance = Instance::resolve_closure(
                                    bx.cx().tcx(),
                                    def_id,
                                    substs,
                                    ty::ClosureKind::FnOnce,
                                )
                                .expect("failed to normalize and resolve closure during codegen")
                                .polymorphize(bx.cx().tcx());
                                OperandValue::Immediate(bx.cx().get_fn_addr(instance))
                            }
                            _ => bug!("{} cannot be cast to a fn ptr", operand.layout.ty),
                        }
                    }
                    mir::CastKind::Pointer(PointerCast::UnsafeFnPointer) => {
                        // This is a no-op at the LLVM level.
                        operand.val
                    }
                    mir::CastKind::Pointer(PointerCast::Unsize) => {
                        assert!(bx.cx().is_backend_scalar_pair(cast));
                        let (lldata, llextra) = match operand.val {
                            OperandValue::Pair(lldata, llextra) => {
                                // unsize from a fat pointer -- this is a
                                // "trait-object-to-supertrait" coercion.
                                (lldata, Some(llextra))
                            }
                            OperandValue::Immediate(lldata) => {
                                // "standard" unsize
                                (lldata, None)
                            }
                            OperandValue::Ref(..) => {
                                bug!("by-ref operand {:?} in `codegen_rvalue_operand`", operand);
                            }
                        };
                        let (lldata, llextra) =
                            base::unsize_ptr(&mut bx, lldata, operand.layout.ty, cast.ty, llextra);
                        OperandValue::Pair(lldata, llextra)
                    }
                    mir::CastKind::Pointer(PointerCast::MutToConstPointer)
                    | mir::CastKind::Misc
                        if bx.cx().is_backend_scalar_pair(operand.layout) =>
                    {
                        if let OperandValue::Pair(data_ptr, meta) = operand.val {
                            if bx.cx().is_backend_scalar_pair(cast) {
                                let data_cast = bx.pointercast(
                                    data_ptr,
                                    bx.cx().scalar_pair_element_backend_type(cast, 0, true),
                                );
                                OperandValue::Pair(data_cast, meta)
                            } else {
                                // cast to thin-ptr
                                // Cast of fat-ptr to thin-ptr is an extraction of data-ptr and
                                // pointer-cast of that pointer to desired pointer type.
                                let llcast_ty = bx.cx().immediate_backend_type(cast);
                                let llval = bx.pointercast(data_ptr, llcast_ty);
                                OperandValue::Immediate(llval)
                            }
                        } else {
                            bug!("unexpected non-pair operand");
                        }
                    }
                    mir::CastKind::DynStar => {
                        let data = match operand.val {
                            OperandValue::Ref(_, _, _) => todo!(),
                            OperandValue::Immediate(v) => v,
                            OperandValue::Pair(_, _) => todo!(),
                        };
                        let trait_ref =
                            if let ty::Dynamic(data, _, ty::DynStar) = cast.ty.kind() {
                                data.principal()
                            } else {
                                bug!("Only valid to do a DynStar cast into a DynStar type")
                            };
                        let vtable = get_vtable(bx.cx(), source.ty(self.mir, bx.tcx()), trait_ref);
                        OperandValue::Pair(data, vtable)
                    }
                    mir::CastKind::Pointer(
                        PointerCast::MutToConstPointer | PointerCast::ArrayToPointer,
                    )
                    | mir::CastKind::Misc
                    // Since int2ptr can have arbitrary integer types as input (so we have to do
                    // sign extension and all that), it is currently best handled in the same code
                    // path as the other integer-to-X casts.
                    | mir::CastKind::PointerFromExposedAddress => {
                        assert!(bx.cx().is_backend_immediate(cast));
                        let ll_t_out = bx.cx().immediate_backend_type(cast);
                        if operand.layout.abi.is_uninhabited() {
                            let val = OperandValue::Immediate(bx.cx().const_undef(ll_t_out));
                            return (bx, OperandRef { val, layout: cast });
                        }
                        let r_t_in =
                            CastTy::from_ty(operand.layout.ty).expect("bad input type for cast");
                        let r_t_out = CastTy::from_ty(cast.ty).expect("bad output type for cast");
                        let ll_t_in = bx.cx().immediate_backend_type(operand.layout);
                        let llval = operand.immediate();

                        let newval = match (r_t_in, r_t_out) {
                            (CastTy::Int(i), CastTy::Int(_)) => {
                                bx.intcast(llval, ll_t_out, i.is_signed())
                            }
                            (CastTy::Float, CastTy::Float) => {
                                let srcsz = bx.cx().float_width(ll_t_in);
                                let dstsz = bx.cx().float_width(ll_t_out);
                                if dstsz > srcsz {
                                    bx.fpext(llval, ll_t_out)
                                } else if srcsz > dstsz {
                                    bx.fptrunc(llval, ll_t_out)
                                } else {
                                    llval
                                }
                            }
                            (CastTy::Int(i), CastTy::Float) => {
                                if i.is_signed() {
                                    bx.sitofp(llval, ll_t_out)
                                } else {
                                    bx.uitofp(llval, ll_t_out)
                                }
                            }
                            (CastTy::Ptr(_) | CastTy::FnPtr, CastTy::Ptr(_)) => {
                                bx.pointercast(llval, ll_t_out)
                            }
                            (CastTy::Int(i), CastTy::Ptr(_)) => {
                                let usize_llval =
                                    bx.intcast(llval, bx.cx().type_isize(), i.is_signed());
                                bx.inttoptr(usize_llval, ll_t_out)
                            }
                            (CastTy::Float, CastTy::Int(IntTy::I)) => {
                                bx.cast_float_to_int(true, llval, ll_t_out)
                            }
                            (CastTy::Float, CastTy::Int(_)) => {
                                bx.cast_float_to_int(false, llval, ll_t_out)
                            }
                            _ => bug!("unsupported cast: {:?} to {:?}", operand.layout.ty, cast.ty),
                        };
                        OperandValue::Immediate(newval)
                    }
                };
                (bx, OperandRef { val, layout: cast })
            }

            mir::Rvalue::Ref(_, bk, place) => {
                let mk_ref = move |tcx: TyCtxt<'tcx>, ty: Ty<'tcx>| {
                    tcx.mk_ref(
                        tcx.lifetimes.re_erased,
                        ty::TypeAndMut { ty, mutbl: bk.to_mutbl_lossy() },
                    )
                };
                self.codegen_place_to_pointer(bx, place, mk_ref)
            }

            mir::Rvalue::CopyForDeref(place) => {
                let operand = self.codegen_operand(&mut bx, &Operand::Copy(place));
                (bx, operand)
            }
            mir::Rvalue::AddressOf(mutability, place) => {
                let mk_ptr = move |tcx: TyCtxt<'tcx>, ty: Ty<'tcx>| {
                    tcx.mk_ptr(ty::TypeAndMut { ty, mutbl: mutability })
                };
                self.codegen_place_to_pointer(bx, place, mk_ptr)
            }

            mir::Rvalue::Len(place) => {
                let size = self.evaluate_array_len(&mut bx, place);
                let operand = OperandRef {
                    val: OperandValue::Immediate(size),
                    layout: bx.cx().layout_of(bx.tcx().types.usize),
                };
                (bx, operand)
            }

            mir::Rvalue::BinaryOp(op, box (ref lhs, ref rhs)) => {
                let lhs = self.codegen_operand(&mut bx, lhs);
                let rhs = self.codegen_operand(&mut bx, rhs);
                let llresult = match (lhs.val, rhs.val) {
                    (
                        OperandValue::Pair(lhs_addr, lhs_extra),
                        OperandValue::Pair(rhs_addr, rhs_extra),
                    ) => self.codegen_fat_ptr_binop(
                        &mut bx,
                        op,
                        lhs_addr,
                        lhs_extra,
                        rhs_addr,
                        rhs_extra,
                        lhs.layout.ty,
                    ),

                    (OperandValue::Immediate(lhs_val), OperandValue::Immediate(rhs_val)) => {
                        self.codegen_scalar_binop(&mut bx, op, lhs_val, rhs_val, lhs.layout.ty)
                    }

                    _ => bug!(),
                };
                let operand = OperandRef {
                    val: OperandValue::Immediate(llresult),
                    layout: bx.cx().layout_of(op.ty(bx.tcx(), lhs.layout.ty, rhs.layout.ty)),
                };
                (bx, operand)
            }
            mir::Rvalue::CheckedBinaryOp(op, box (ref lhs, ref rhs)) => {
                let lhs = self.codegen_operand(&mut bx, lhs);
                let rhs = self.codegen_operand(&mut bx, rhs);
                let result = self.codegen_scalar_checked_binop(
                    &mut bx,
                    op,
                    lhs.immediate(),
                    rhs.immediate(),
                    lhs.layout.ty,
                );
                let val_ty = op.ty(bx.tcx(), lhs.layout.ty, rhs.layout.ty);
                let operand_ty = bx.tcx().intern_tup(&[val_ty, bx.tcx().types.bool]);
                let operand = OperandRef { val: result, layout: bx.cx().layout_of(operand_ty) };

                (bx, operand)
            }

            mir::Rvalue::UnaryOp(op, ref operand) => {
                let operand = self.codegen_operand(&mut bx, operand);
                let lloperand = operand.immediate();
                let is_float = operand.layout.ty.is_floating_point();
                let llval = match op {
                    mir::UnOp::Not => bx.not(lloperand),
                    mir::UnOp::Neg => {
                        if is_float {
                            bx.fneg(lloperand)
                        } else {
                            bx.neg(lloperand)
                        }
                    }
                };
                (bx, OperandRef { val: OperandValue::Immediate(llval), layout: operand.layout })
            }

            mir::Rvalue::Discriminant(ref place) => {
                let discr_ty = rvalue.ty(self.mir, bx.tcx());
                let discr_ty = self.monomorphize(discr_ty);
                let discr = self
                    .codegen_place(&mut bx, place.as_ref())
                    .codegen_get_discr(&mut bx, discr_ty);
                (
                    bx,
                    OperandRef {
                        val: OperandValue::Immediate(discr),
                        layout: self.cx.layout_of(discr_ty),
                    },
                )
            }

            mir::Rvalue::NullaryOp(null_op, ty) => {
                let ty = self.monomorphize(ty);
                assert!(bx.cx().type_is_sized(ty));
                let layout = bx.cx().layout_of(ty);
                let val = match null_op {
                    mir::NullOp::SizeOf => layout.size.bytes(),
                    mir::NullOp::AlignOf => layout.align.abi.bytes(),
                };
                let val = bx.cx().const_usize(val);
                let tcx = self.cx.tcx();
                (
                    bx,
                    OperandRef {
                        val: OperandValue::Immediate(val),
                        layout: self.cx.layout_of(tcx.types.usize),
                    },
                )
            }

            mir::Rvalue::ThreadLocalRef(def_id) => {
                assert!(bx.cx().tcx().is_static(def_id));
                let static_ = bx.get_static(def_id);
                let layout = bx.layout_of(bx.cx().tcx().static_ptr_ty(def_id));
                let operand = OperandRef::from_immediate_or_packed_pair(&mut bx, static_, layout);
                (bx, operand)
            }
            mir::Rvalue::Use(ref operand) => {
                let operand = self.codegen_operand(&mut bx, operand);
                (bx, operand)
            }
            mir::Rvalue::Repeat(..) | mir::Rvalue::Aggregate(..) => {
                // According to `rvalue_creates_operand`, only ZST
                // aggregate rvalues are allowed to be operands.
                let ty = rvalue.ty(self.mir, self.cx.tcx());
                let operand =
                    OperandRef::new_zst(&mut bx, self.cx.layout_of(self.monomorphize(ty)));
                (bx, operand)
            }
            mir::Rvalue::ShallowInitBox(ref operand, content_ty) => {
                let operand = self.codegen_operand(&mut bx, operand);
                let lloperand = operand.immediate();

                let content_ty = self.monomorphize(content_ty);
                let box_layout = bx.cx().layout_of(bx.tcx().mk_box(content_ty));
                let llty_ptr = bx.cx().backend_type(box_layout);

                let val = bx.pointercast(lloperand, llty_ptr);
                let operand = OperandRef { val: OperandValue::Immediate(val), layout: box_layout };
                (bx, operand)
            }
        }
    }

    fn evaluate_array_len(&mut self, bx: &mut Bx, place: mir::Place<'tcx>) -> Bx::Value {
        // ZST are passed as operands and require special handling
        // because codegen_place() panics if Local is operand.
        if let Some(index) = place.as_local() {
            if let LocalRef::Operand(Some(op)) = self.locals[index] {
                if let ty::Array(_, n) = op.layout.ty.kind() {
                    let n = n.eval_usize(bx.cx().tcx(), ty::ParamEnv::reveal_all());
                    return bx.cx().const_usize(n);
                }
            }
        }
        // use common size calculation for non zero-sized types
        let cg_value = self.codegen_place(bx, place.as_ref());
        cg_value.len(bx.cx())
    }

    /// Codegen an `Rvalue::AddressOf` or `Rvalue::Ref`
    fn codegen_place_to_pointer(
        &mut self,
        mut bx: Bx,
        place: mir::Place<'tcx>,
        mk_ptr_ty: impl FnOnce(TyCtxt<'tcx>, Ty<'tcx>) -> Ty<'tcx>,
    ) -> (Bx, OperandRef<'tcx, Bx::Value>) {
        let cg_place = self.codegen_place(&mut bx, place.as_ref());

        let ty = cg_place.layout.ty;

        // Note: places are indirect, so storing the `llval` into the
        // destination effectively creates a reference.
        let val = if !bx.cx().type_has_metadata(ty) {
            OperandValue::Immediate(cg_place.llval)
        } else {
            OperandValue::Pair(cg_place.llval, cg_place.llextra.unwrap())
        };
        (bx, OperandRef { val, layout: self.cx.layout_of(mk_ptr_ty(self.cx.tcx(), ty)) })
    }

    pub fn codegen_scalar_binop(
        &mut self,
        bx: &mut Bx,
        op: mir::BinOp,
        lhs: Bx::Value,
        rhs: Bx::Value,
        input_ty: Ty<'tcx>,
    ) -> Bx::Value {
        let is_float = input_ty.is_floating_point();
        let is_signed = input_ty.is_signed();
        match op {
            mir::BinOp::Add => {
                if is_float {
                    bx.fadd(lhs, rhs)
                } else {
                    bx.add(lhs, rhs)
                }
            }
            mir::BinOp::Sub => {
                if is_float {
                    bx.fsub(lhs, rhs)
                } else {
                    bx.sub(lhs, rhs)
                }
            }
            mir::BinOp::Mul => {
                if is_float {
                    bx.fmul(lhs, rhs)
                } else {
                    bx.mul(lhs, rhs)
                }
            }
            mir::BinOp::Div => {
                if is_float {
                    bx.fdiv(lhs, rhs)
                } else if is_signed {
                    bx.sdiv(lhs, rhs)
                } else {
                    bx.udiv(lhs, rhs)
                }
            }
            mir::BinOp::Rem => {
                if is_float {
                    bx.frem(lhs, rhs)
                } else if is_signed {
                    bx.srem(lhs, rhs)
                } else {
                    bx.urem(lhs, rhs)
                }
            }
            mir::BinOp::BitOr => bx.or(lhs, rhs),
            mir::BinOp::BitAnd => bx.and(lhs, rhs),
            mir::BinOp::BitXor => bx.xor(lhs, rhs),
            mir::BinOp::Offset => {
                let pointee_type = input_ty
                    .builtin_deref(true)
                    .unwrap_or_else(|| bug!("deref of non-pointer {:?}", input_ty))
                    .ty;
                let llty = bx.cx().backend_type(bx.cx().layout_of(pointee_type));
                bx.inbounds_gep(llty, lhs, &[rhs])
            }
            mir::BinOp::Shl => common::build_unchecked_lshift(bx, lhs, rhs),
            mir::BinOp::Shr => common::build_unchecked_rshift(bx, input_ty, lhs, rhs),
            mir::BinOp::Ne
            | mir::BinOp::Lt
            | mir::BinOp::Gt
            | mir::BinOp::Eq
            | mir::BinOp::Le
            | mir::BinOp::Ge => {
                if is_float {
                    bx.fcmp(base::bin_op_to_fcmp_predicate(op.to_hir_binop()), lhs, rhs)
                } else {
                    bx.icmp(base::bin_op_to_icmp_predicate(op.to_hir_binop(), is_signed), lhs, rhs)
                }
            }
        }
    }

    pub fn codegen_fat_ptr_binop(
        &mut self,
        bx: &mut Bx,
        op: mir::BinOp,
        lhs_addr: Bx::Value,
        lhs_extra: Bx::Value,
        rhs_addr: Bx::Value,
        rhs_extra: Bx::Value,
        _input_ty: Ty<'tcx>,
    ) -> Bx::Value {
        match op {
            mir::BinOp::Eq => {
                let lhs = bx.icmp(IntPredicate::IntEQ, lhs_addr, rhs_addr);
                let rhs = bx.icmp(IntPredicate::IntEQ, lhs_extra, rhs_extra);
                bx.and(lhs, rhs)
            }
            mir::BinOp::Ne => {
                let lhs = bx.icmp(IntPredicate::IntNE, lhs_addr, rhs_addr);
                let rhs = bx.icmp(IntPredicate::IntNE, lhs_extra, rhs_extra);
                bx.or(lhs, rhs)
            }
            mir::BinOp::Le | mir::BinOp::Lt | mir::BinOp::Ge | mir::BinOp::Gt => {
                // a OP b ~ a.0 STRICT(OP) b.0 | (a.0 == b.0 && a.1 OP a.1)
                let (op, strict_op) = match op {
                    mir::BinOp::Lt => (IntPredicate::IntULT, IntPredicate::IntULT),
                    mir::BinOp::Le => (IntPredicate::IntULE, IntPredicate::IntULT),
                    mir::BinOp::Gt => (IntPredicate::IntUGT, IntPredicate::IntUGT),
                    mir::BinOp::Ge => (IntPredicate::IntUGE, IntPredicate::IntUGT),
                    _ => bug!(),
                };
                let lhs = bx.icmp(strict_op, lhs_addr, rhs_addr);
                let and_lhs = bx.icmp(IntPredicate::IntEQ, lhs_addr, rhs_addr);
                let and_rhs = bx.icmp(op, lhs_extra, rhs_extra);
                let rhs = bx.and(and_lhs, and_rhs);
                bx.or(lhs, rhs)
            }
            _ => {
                bug!("unexpected fat ptr binop");
            }
        }
    }

    pub fn codegen_scalar_checked_binop(
        &mut self,
        bx: &mut Bx,
        op: mir::BinOp,
        lhs: Bx::Value,
        rhs: Bx::Value,
        input_ty: Ty<'tcx>,
    ) -> OperandValue<Bx::Value> {
        // This case can currently arise only from functions marked
        // with #[rustc_inherit_overflow_checks] and inlined from
        // another crate (mostly core::num generic/#[inline] fns),
        // while the current crate doesn't use overflow checks.
        if !bx.cx().check_overflow() {
            let val = self.codegen_scalar_binop(bx, op, lhs, rhs, input_ty);
            return OperandValue::Pair(val, bx.cx().const_bool(false));
        }

        let (val, of) = match op {
            // These are checked using intrinsics
            mir::BinOp::Add | mir::BinOp::Sub | mir::BinOp::Mul => {
                let oop = match op {
                    mir::BinOp::Add => OverflowOp::Add,
                    mir::BinOp::Sub => OverflowOp::Sub,
                    mir::BinOp::Mul => OverflowOp::Mul,
                    _ => unreachable!(),
                };
                bx.checked_binop(oop, input_ty, lhs, rhs)
            }
            mir::BinOp::Shl | mir::BinOp::Shr => {
                let lhs_llty = bx.cx().val_ty(lhs);
                let rhs_llty = bx.cx().val_ty(rhs);
                let invert_mask = common::shift_mask_val(bx, lhs_llty, rhs_llty, true);
                let outer_bits = bx.and(rhs, invert_mask);

                let of = bx.icmp(IntPredicate::IntNE, outer_bits, bx.cx().const_null(rhs_llty));
                let val = self.codegen_scalar_binop(bx, op, lhs, rhs, input_ty);

                (val, of)
            }
            _ => bug!("Operator `{:?}` is not a checkable operator", op),
        };

        OperandValue::Pair(val, of)
    }
}

impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
    pub fn rvalue_creates_operand(&self, rvalue: &mir::Rvalue<'tcx>, span: Span) -> bool {
        match *rvalue {
            mir::Rvalue::Ref(..) |
            mir::Rvalue::CopyForDeref(..) |
            mir::Rvalue::AddressOf(..) |
            mir::Rvalue::Len(..) |
            mir::Rvalue::Cast(..) | // (*)
            mir::Rvalue::ShallowInitBox(..) | // (*)
            mir::Rvalue::BinaryOp(..) |
            mir::Rvalue::CheckedBinaryOp(..) |
            mir::Rvalue::UnaryOp(..) |
            mir::Rvalue::Discriminant(..) |
            mir::Rvalue::NullaryOp(..) |
            mir::Rvalue::ThreadLocalRef(_) |
            mir::Rvalue::Use(..) => // (*)
                true,
            mir::Rvalue::Repeat(..) |
            mir::Rvalue::Aggregate(..) => {
                let ty = rvalue.ty(self.mir, self.cx.tcx());
                let ty = self.monomorphize(ty);
                self.cx.spanned_layout_of(ty, span).is_zst()
            }
        }

        // (*) this is only true if the type is suitable
    }
}